This invention relates to an industrial manipulator device and in particular to an operational element thereof. An operational element may comprise a functional zone for example a claw or hand mechanism suitable for use in transporting articles and the operational use with which this invention is particularly concerned, is the stacking of articles in close proximity to adjacent articles, hereinafter referred to as "close-packing".
The term "industrial manipulator" is used to describe a robot-like machine capable of moving an "operational element" to a location on a space grid, the movement is determined by commands received by the industrial manipulator and translated into controlled movements imparted to the operational element for example by powered joints. For example the commands may come from an operator e.g. via a manual control lever or from an electronic keyboard or they may come from a memory unit.
Such industrial manipulators will in general be capable of positioning any defined point of the operational element (e.g. a functional extremity) or of the articles carried thereby at any desired point on a three-dimensional space grid. This positioning operation requires three degrees of freedom for movements along or in three mutually perpendicular axes or planes irrespective of how these movements are obtained e.g. either circularly or linearly. In additional industrial manipulators are known which impart to the operational element a rotational movement about one of the axes or planes of the space grid so that having positioned the operational element and any article carried thereby, the operational element and article may together be rotated about one of the axes on the space grid in order to orientate the article for locating it into a shaped slot, bed or other receiver. The term "orientation" is used to describe the rotation of the operational element about one of the mutually perpendicular space grid axes and constitutes an additional degree of freedom in industrial manipulators provided that the orientation is effected independently of the three positional movements used to locate the operational element in the space grid.
The "functional zone" of the operational element may include a cutting tool, assembly tool, gripper, load-supporting platform, welding electrode, paint spray or other component well known in the production engineering art and the method of support control or mechanical attachment to the operation element.
A problem has been observed in the use of such conventional industrial manipulator devices and operational elements thereof using a gripper as the functional zone for the picking up and close-packing of articles, for example--the picking up and stacking of bags or sacks filled with powder or granular material onto a pallet (hereinafter called "Palletization"). For simplicity palletization is considered to be in one plane of the space grid, most conveniently the horizontal plane. Articles, after picking up, can be positioned and orientated by four degrees of freedom (three positions in grid space and orientation by a rotary movement in the plane of the pallet). This locates each one on a pallet but when this is done, the thickness of the gripper fingers prevents the close-packing operations being performed exactly and gently, especially if the gripper has curved fingers, as many do have in order to give a better grip. In known palletization, the articles are often positioned fairly closely and dropped or otherwise propelled (e.g. from an expulsion piston in the claw) into location as the gripper opens to release the article but these procedures have disadvantages because the article may not withstand the rough treatment.
We have now found that an operational element having an additional movement may be made such that either a minimum of five degrees of freedom (i.e. three positional motions and two orientational motions all independent of each other) or four degrees of freedom (i.e. three positional motions and one orientational motion all independent of each other) together with a fifth motion which combines independent rotation with a separately-controlled but consequential positional motion is essential to provide adequate control of the operational element (or the functional zone) for some delicate operations to be performed. This novel device on an industrial manipulator when the functional zone is a gripper enables palletization to be performed gently and with precision even when curved fingers to the gripper would prevent the effective use of a device having only four degrees of freedom.